Colombia. A beautiful country full of natural wonders, forests, exotic birds and... hippos? Yes, hippos, the ones from Africa. No joke — the country is facing a huge hippo problem.
Colombia boasts the biggest hippo population outside of Africa. Different estimates point to something between 90 and 180 animals, but there are still doubts about the real number.
"What worries me more about this is that the population has continued to grow exponentially," German Jimenez, a biology professor at the Pontifical Javierian University in the Colombian capital, Bogota, told DW.
So, what's going on in Colombia?
Pablo Escobar, cocaine and hippos
The actions of Pablo Escobar, an infamous drug lord who terrorized Colombia during the 1980s and early 1990s, resulted in thousands of deaths.
In the 1980s, he smuggled four hippos from a wildlife park in Dallas, Texas, into his new exotic zoo east of Medellin, Colombia's second-largest city.
They became part of his massive 2,000-hectare (roughly 5,000-acre) Hacienda Napoles ranch in Puerto Triunfo, which comprised a Spanish colonial house, a landing strip, many artificial lakes, roads and even its own gas station.
Escobar wanted a truly exotic wildlife park, so he also brought rhinos, elephants, giraffes, ostriches and many more animals, calling it his "own Noah’s Ark."
In 1993, Colombian security forces shot and killed Escobar in Medellin. After his death, many of the exotic animals went to other zoos or parks, but the hippos stayed at the hacienda — and eventually escaped, to a place where they probably felt quite at home.
The Hacienda Napoles, which is now a state-owned theme park, is very close to the Magdalena River, one of the country's major arteries, and the river basin shares similarities with the hippos' native ecosystem in various African countries.
A perfect place for hippos
With the ideal place to breed and a lack of government action, the hippo population grew fast.
"Colombia had the opportunity to [control their population] but failed and let the problem grow," said Jimenez.
The hippos In Colombia have no competitors and no predators. They enjoy steadier weather and water levels than in Africa, where intense droughts act as population control.
Basically, the animals can eat and mate all year round in Colombia. Meanwhile in Africa, the number of hippos has dropped sharply since the 1970s. In 2016, the International Union for Conservation of Nature listed them as "vulnerable," the last classification before "endangered."
There are now seven identified hippo population groups along the Magdalena basin, according to a new report by Colombia's Humboldt Institute and the National Science Institute that was commissioned by the Environment Ministry.
"They can start reproducing really young. They can have calves very frequently, like once or more a year. And they can reproduce for a very long time, 50 years, almost to the end of their lifespan," Amanda Subalusky, a biology professor at the University of Florida, told DW.
Subalusky and Jimenez worked together on a study published last month in the journal Scientific Reports, in which they stressed the urgency of the issue and examined potential solutions, as well as their costs.
A love/hate relationship
But what's the problem with Colombia's hippos? Couldn't we just leave them be?
"They're reproducing and growing very fast and relatively soon there's going to be a whole lot of hippos," said Subalusky.
The problem with invasive species is that they can seriously affect wildlife, the local ecosystem, the landscape and also the people of their new home.
Hippos are very territorial and can be very aggressive. In fact, they are well-known in Africa for being one of the deadliest animals, with estimates saying they kill around 500 people every year.
Although no one has been reported killed by hippos in Colombia to date, there have been incidents of attacks and crashes with vehicles. The low population density, according to scientists, is the likely reason for the low number of attacks.
Hippos are a concern for farmers as well because they can destroy fences, consume crops and grass, and sometimes even run over calves.
However, the animals are also a way to make a living for some communities that live around Napoles.
"They defend them a lot," said Jimenez. But the further away from the Hacienda you go, the more people are afraid of hippos, he added.
Huge environmental problem
Then there's the environmental aspect.
Hippos eat around 50 kilograms (110 pounds) of plants a day. That’s a heavy toll on the local vegetation, which has never experienced such a level of herbivory before.
"They are strongly affecting the ecosystems of the Middle Magdalena," said Jimenez. The animals' heavy weight can change the landscape as they walk around.
And because hippos are so big and eat so much, well, they also poop a lot. Since so much dung ends up in rivers, the extra nutrients it releases into the water can lead to algae blooms. This can deplete the water's oxygen content, which is essential for fish survival.
Hippos are what scientists refer to as ecosystem engineers because of how drastically they can alter the landscape. Like beavers in the forests of North America, these engineers play a vital role in many ecosystems. But they can wreak havoc in a foreign environment.
"They [the hippos] must be removed from the basin," said Jimenez.
Hippos declared an invasive species
The fact that not everyone agrees with that became clear in 2009, when the government ordered the death of a hippo called Pepe that was posing a threat to locals. Pepe's death sparked a public outcry, and in 2012 a law was passed making it illegal to kill hippos.
Only subsistence hunting, or hunting for food in communities that rely on it, is permitted in Colombia, explained Jimenez.
Since Pepe, authorities have been trying, unsuccessfully, to limit hippos' numbers by chemically sterilizing them or castrating them. This is a hard task given their immense size, aggression and internal testicles.
"This process entails hippos being captured, anesthetized, transported by helicopter, and surgically operated upon; thus, it is very challenging and can be dangerous for both the people and hippos involved," according to Subalusky and Jimenez’s study.
In 2022, the Colombian government passed a new law declaring hippos an invasive species. The law is now being contested by animal rights groups because it contradicts previous legislation protecting hippos. There's also been discussions about flying the hippos to other countries.
It's a complex problem with environmental, scientific, social, legal and ethical angles. "You’ll never make everybody happy," said Subalusky.
So what can be done about the hippos?
If no action is taken, hippo numbers in Colombia could grow to more than 1,000 by 2035, recent estimates suggest.
Subalusky and Jimenez's study said all hippos need to go, stating that with the current legal situation, the most cost-effective option would be to continue male sterilization. They estimated the costs between $0.85 and 1.4 million (up to €1.3 million), but eradication would take at least 45 years.
However, the researchers showed that using veterinary-assisted euthanasia would be the most effective and fastest solution. They estimate that the whole hippo population could be euthanized in a single year for around $0.61 million.
The plan of action that the Humboldt Institute and the National Science Institute sent the government suggests both social measures and direct interventions.
Informing local communities about the hippos' biology would be one of the social measures, as would be education and collaboration with people to teach them how to live alongside hippos and lessen the animals' negative impact.
The interventions proposed included relocating the hippos to other places, like zoos or wildlife reserves in and outside the country, to keep them in constrained areas, or culling them.
After this report, the Environment and Sustainable Development Ministry published a press release on April 14 that said it was "working on the management plan to be adopted for this species in the country."
Scientists agree that the growth rate of hippos is worrying, and that the longer the Colombian government waits, the harder it's going to be to control the animals. Any delay could have serious consequences for the Magdalena River basin and for the people living there.
Edited by: Carla Bleiker